Implantable medical devices (IMDs) are used to produce therapeutic results in a patient and for monitoring physiologic parameters of a patient. Examples of IMDs include implantable drug infusion pumps, implantable neurostimulators, implantable cardioverter defibrillators, implantable cardiac pacemakers, and cochlear implants. Most of these IMDs often provide an electrical output or contain electrical circuitry to perform their intended functions. These devices are typically powered by a battery contained within the housing of the implantable medical device.
Cobalt/Nickel alloys are known and are often used in IMDs. For example, MP35N (35% Ni, 20% Cr, 10% Mo and approximately 35% Co by weight) is a cobalt based multi-phase alloy with excellent mechanical properties and corrosion resistance. MP35N has been used, for example, in conductor coils, spinal products, stents and various parts in implantable infusion pumps.
Release of Ni from an alloy, such as MP35N, is a concern because a small percentage of the general population shows Ni sensitivity. Co ion release is also a concern for electrical leads because, for example, polyurethane insulation about the lead may be subjected to metal ion oxidation (MIO). This oxidation can cause the polyurethane to degrade and allow for shorting of the electrode under physiological conditions.
Therefore, a need exists for a process and materials that overcomes one or more of the current disadvantages noted above.